Chemical Coordination In Plants Flashcards
What are hormones of plants known as?
Phytohormones
What is the main auxin found in plants?
IAA (Indole 3 acetic-acid)
What is Tropism?
The biological phenomena of growth or body movements of an organism in response to an environmental stimulus is known as tropism
What is Phototropism?
Phototropism is the movement of plants towards the stimulus of light.
Shoots of plants are positively phototropic (they move towards light) whereas the roots of plants are negatively phototropic (move away).
What is geotropism?
It means growing of plants towards the earth’s gravity. Also known as Gravitropism. Plant parts growing towards gravity are positively geotropic (e.g root tip) and those parts that grow away from gravity are negatively geotropic (e.g. shoot tip)
What is Hydrotropism?
The movement of plant parts in response to water or moisture.
Positively Hydrotropic - Roots
Negatively Hydrotropic - shoots
What is thigmotropism?
The growth movement of plant parts in response to touch stimulus.
Eg. Cuscuta and vines have tendrils which coil around other plants.
What is ChemoTropism?
ChemoTropism is the phenomenon of growth of plant organs in response to chemicals.
Eg. Movement of pollen tube of angiosperms and gymnosperms towards sugars and peptones secreted by neck canal cells of the female gametophyte.
- movement of fungi growing towards the areas Richer in foods
- tentacles of drosera towards source of nutrition.
What is heliotropism?
•Exhibited by Sunflowers.
•sunflower heads follow the sun from east to west direction
•caused due to auxins sensitive to light.
What is parthenocarpy?
Fruit formation without fertilization. Caused by auxins. Eg. Apples, tomatoes, bananas.
State four functions of auxins
- It delays leaf senescence
- It promotes growth of stems, roots and fruits by cell- elongation
- Auxins promote the growth of apical buds and inhibit growth of lateral buds.
- Auxins induce rooting in the cutting of some plants like rose, bougainvillea
Which form of Gibberelin is most studied?
GA3 form
Where are gibberlins mainly found in plants?
Meristematic regions like stem-apex, root-apex, buds, seeds
State 4 functions of gibberelins
- main function is to promote growth of internodes by cell elongation
- they break seed dormancy and initiate germination
- promote fruit growth and capable of parthenocarpy
- delay senescence
Who discovered cytokinins?
Discovered by Skoog and Miller in 1950
Where are cytokinins found?
Seeds, developing fruits, embryo
State 4 functions of cytokinins
- They break seed dormancy
- Stimulate plant growth by cell division
(Auxins and gibberlins - cell elongation) - Expansion of cotyledons in seeds
- Promote chlorophyll synthesis in chloroplast and delay senescence
- Inhibit Apical Dominance
Which is the ham hormone at room temp.? What are its two main processes?
Ethylene.
Tow main processes are -
•Reduction in stem elongation
•acceleration of senescence
Which hormone is most widely used in Agriculture?
Ethylene
State 4 functions of ethylene
- Ripening of fruits
- Initiating germination in peanut seeds
- Sprouting of potato tuber
- Promoting root growth and root hair formation
- Inducing flowering in mango
Which is the growth Retarding Hormone?
It what kind of plants is it found?
Abscisic Acid (ABA). It’s found in Angiosperms, gymnosperms, pteridophytes, and some mosses. Fruits and seeds contain highest amount of ABA
State 4 functions of ABA
- Induces dormancy of buds and seeds
- Inhibits seed-germination and development
- Stimulates closing of stomata
- Accelerated
What is the site of synthesis for auxins?
Synthesized in shoot apical meristems and young leaves
What is the site of synthesis for gibberelins?
Meristems of apical buds and roots
What is the site of synthesis for cytokininsv
Roots and transported to other organs
What is the site of synthesis for Ethylene?
In senescent leaves and flowers, germinating seeds and ripening Fruits.
What is the site of synthesis for abscisic acid?
In green fruits and seeds at beginning of wintering period
